Lightning arrester



Feb. 10, 1953 C, W, PETERSEN 2,628,323

LIGHTNING ARRESTER Filed Nov. 5. 1951 Z/o l, Wfl r'sen B HZZor-nyPatented Feb. 10, 1953 UNITED STATES ETENT OFFICE LIGHTNING ARRESTERClifford W. Petersen, Wauwatosa, Wis., assignor to McGraw ElectricCompany, Milwaukee, Wis., a corporation of Delaware Application November3, 1951, Serial No. 254,707

(Cl. S13- 243) 11 Claims. l

This invention relates to an improvement in lightning arresters, for theprotection of electrical distribution systems and conductors, and inparticular to an improvement in electrodes used in spark gaps.

It has been found that spark gaps using electrodes in a ladder-likeformation between insulating spacers operate more effectively when a lowimpulse ratio can be achieved. A low impulse ratio makes it possible tohave greater uniformity oi spark-over between the electrodes, thusallowing the excess current to be more readily dissipated.

To obtain a low impulse ratio, some form of ionizing radiation must bepresent. This radiation is emitted from discharges existing between theelectrodes and the insulating spacer aoco-. panying the dielectricdisplacement current. The intensity of this radiation is proportional tothe dielectric displacement current so that spark gaps with spacers oihigh dielectric constant material give lower impulse ratios.

it is an object of this invention to provide an improved condition foruniform spark-over.

Another object o this invention is to provide a means of holding theelectrodes tightly against the insulating spacer.

It is also an object of this invention to provide an electrode for alightning arrester in which expansion and contraction due to thermaldifferences between the various materials is taken care of to insure aiirm contact between the electrode and the spacer.

And in particular it is an object of this invention to provide anelectrode that contacts the insulating bushing in such a manner so thatthe dielectric eld set up by the electrodes will create an area ofradiation in the air spaces between the electrodes.

Other objects will appear from time to time in the course of thespecification and claims.

l illustrate my invention more or less symbolically in the accompanyingdrawing, in which:

Fig. l is a standard spark gap shown partly in section with my improvedelectrode incorporated.

Fig. 2 is an enlarged view of my improved electrode illustrating thedielectric elds and the area of radiation.

Fig. 3 is an enlarged View of a variation of my improved electrodeillustrating the dielectric elds and the area of radiation.

Like reference gures illustrate like parts throughout.

In Fig. 1, I show my improved electrode incorporated in a standardspark-gap consisting of a housing I which is tubular and has a straight.bore 2 throughout. This housing I is partially nlled with a granularmaterial 3 such as silicon carbide and is provided with a lower plate 4and an upper plate 5 at opposite ends of the granular mass 3. The lowerplate is sealed in place by means of a soft metal seal '6 bonding thestranded portions of a ground conductor 'i to the metal plate 4 and alsoconforming to the interior of 'r the housing I, and a rubber annularwedgeshaped gasket 8 spaced from the granular material. The lowerportion of the arrester is completed by providing an asphalt seal 9 anda sulphur compound seal I0, although other sealing means may be used ifdesired.

The upper plate 5 has soft metal II molded in place above it. The upperend of the housing is closed by a spring copper cap I2 which hasdownwardly turned flanges I2a overhanging the upper edge of the housing.These flanges have a soit metal I3 poured into place and molded asshown, in interlocking relation with the housing or so as to hold themetal cap under tension and thereby transmit tension downwardly throughthe spark gap, hereinalter described, to the granular material.

'lhe device may be covered by an insulating cap I4 with an asphaltcement l5 poured between the flanges 12a and the cap I4. A lineconductor i6 is bonded in place to the metal cap l2 by the soft metalseal.

A round headed upper screw I'I ts within a recess in the cap I4 andpasses through the upper end member or plate I8 of the spark gap andinto the uppermost electrode at I9. This screw I'I locks the spark gapassembly together to make a unitary structure.

Within the housing I is a pair of insulating uprights 2l of someinsulating material such as steatite. These uprights 2l form a spacingdevice for the electrode of the spark gap by means of machined openings22 which provide the ladder-like supports for the electrodes 23.

These electrodes 23 consist of solid turned metal, either brass or someother suitable material. Referring to Fig. 2, the middle wider portionhas tapered ends 24 and the two extremities 25 are machined to a smallerdiameter to iit into the series of openings 22 in the insulatinguprights 2|.

The extremities 25 of the electrode are sulciently smaller than theopening 22 in the uprights 2l so that a split eyelet 26 can be insertedaround the extremities 25, and within the opening 22. This split eyeletis of such a size as to 3 make a rm contact between the extremities 25oi the electrode 23 and the uprights 2l and because of the split it hasa spring action which insures this contact.

Where the metal and the insulation meet in sharp contact within thespacer and on its surface, a dielectric fringe eiTect is set up as shownat 2l in Fig. 2. This fringe eiect causes a dielectric ield 23 withinthe insulating uprights 2i between the contact points. The dielectricneld sets up ionization and it is the radiation 29 of the ions extendingacross the air gaps between the electrodes that produces a Steadyingeect on the spark-over. These lines of radiation tend to eliminateerratic spark-over.

In Fig. 3, I show a variant form of electrode to achieve a similarresult. In this form the electrode 3D has an integral washer on one endand in the opposite end has a bore 3l through its middle sectionentending somewhat more than half way through the electrode. Theelectrode shank 32 is a separate piece with a washer 33 integral withit. It is inserted into the bore along with a spring 35. This springaction holds the washers 33 at both ends in firm Contact the eyelet 2Sof Fig. 2 or the spring means 34 of Fig. 3, the radiation means isintensied and uniform. With this great improvement in the area ofradiation between the electrodes, the spark-over becomes uniform and alow impulse ratio can be heid. Wnen lightning strikes along the line, itis quickly and evenly dissipated through this improved lightningarrester.

I claim:

1. In a spark gap, a series of electrodes arranged in ladder-likeconstruction between two upright insulating spacers, a member havinguniform contact surface between the electrode and the insulating spacersto provide positive ioniz ing radiation within the gap.

2. In a spark gap, a series of electrodes arranged in ladder-likeconstruction between two upright insulating spacers, a tension eyeletinserted between the electrode and the insulating spacer to create a rmcontact between them, the points of contact between the electrodestension eyelet and insulation, setting up a dielectric eld between theelectrodes, said dielectric eld causing ionization which radiates to theair spaces between the electrodes.

3. In a spark gap, a series of electrodes arranged in ladder-likeconstruction between two upright insulating spacers, a split eyeletinserted between the electrode and the insulating spacer to create a rmcontact between them, the points of contact between the electrodeseyelet and insulation setting up a dielectric field between theelectrodes, said dielectric eld causing ionization which radiates to theair spaces between the electrodes, said lines of ionized radiationcausing a uniform spark over between the electrodes.

4. In a spark gap, a series of electrodes arranged in ladder-likeconstruction between two upright insulating spacers, a flanged tensioneyelet inserted between the electrode and the insulating spacer tocreate a firm contact between them, the points of contact between theelectrodes said tension eyelet and insulation, setting up a dielectriceld between the electrodes, said dielectric eld causing ionization whichradiates to the air spaces between the electrodes, said lines of ionizedradiation allowing a low impulse ratio in the spark gap.

`5. In a spark gap, a series of electrodes spaced vertically, the endsof the electrodes inserted in openings in an insulating spacer, a splitmetal eyelet inserted between the electrode ends and the openings in theinsulating spacer and making a rm Contact between them.

6. In a spark gap, a series of electrodes spaced vertically, the ends ofthe electrodes inserted in openings in insulating spacers, a split metaleyelet inserted between the electrode ends and the openings in theinsulating spacer making a rm contact between them, the contact pointsbetween the eyelet and the insulation setting up a dielectric fieldbetween contact points of adjacent electrodes, said dielectric eldemitting ionized radiation into the air spaces between the electrodes.

'7. In a spark gap, a ladder-like series of electrodes, with machinedends that fit into openings in insulating spacers, a combination spliteyelet washer and sleeve tted under tension between the ends of theelectrode and the opening in said insulating spacer.

8. In a spark gap, a ladder-like series of electrodes, with machinedends that fit into openings in insulating spacers, a combination spliteyelet washer and sleeve tted under tension between the ends of theelectrode and the opening in said insulating spacer, the said tensioncausing a rm nt between electrode, washer, and insulating spacer.

9. In a spark gap, a ladder-like series of electrodes, with machinedends that t into openings in insulating spacers, a combination spliteyelet washer and sleeve tted under tension between the ends of theelectrode and the opening in said insulating spacers, the said tensioncausing a nrm t between electrode, washer, and insulating spacers, whenthermal changes cause uneven expansion and contraction of the variousparts.

10. In a spark gap, a ladder-like series of electrodes, with machinedends that fit into openings in insulating spacers, a combination spliteyelet washer and sleeve iitted under tension between the ends of theelectrode and the opening in said insulating spacers, the said tensioncausing a firm nt between electrode, washer, and insulating spacers,which makes the ionization constant and the spark over uniform.

11. In a spark gap, a ladder-like series of electrodes, the ends of saidelectrodes inserted in openings in two upright insulating spacers, saidelectrodes consisting of one end of smaller diameter than the middleportion and having an integral washer, contacting the inner side of oneinsulating spacer, a bore extending inwardly through the electrode fromits other side, said bore holding a spring and a piston-like member withintegral washer, said piston-like member contacting the spring on itsinner end and the insulating spacer on its outer end, the spring meansthrusting outwardly the two ends with their integral washers making a:drm contact between washer and insulating spacer.

CLIFFORD W. PETERSEN.

No references cited.

